Classification and selection of stepper motors

I.Classification of stepper motors
1. Open loop stepper motor and closed loop stepper motor.
open-loop stepper motor
close-loop stepper motor
2. The difference between an open loop stepper motor and a closed loop stepper motor
a. Feedback
The fundamental difference between open loop and closed loop is whether it will feedback the current running status signal. Open loop has no feedback signal, so it is only executed in sequence, while for closed loop feedback signal, the stepper motor driver takes corresponding action measures or signal feedback according to the signal. For the PLC, the PLC decides the next program processing.
b. Output impact

Open-loop control system: If there is no feedback loop between the output and input of the system, the output has no influence on the control effect of the system, and such a system becomes an open-loop control system.

Closed-loop control system: The feedback control system is also called a closed-loop control system, and the output has a direct influence on the control effect.

Such as: automatic temperature adjustment air conditioner, when the ambient temperature is higher than the set temperature, the air conditioning refrigeration system will automatically turn on and adjust the room temperature to the set value.
c. control method

Closed-loop control methods are roughly divided into two types:

(1). Keep the phase relationship between the excitation magnetic flux and the current consistent, so that it can generate electromagnetic torque that can drive the load torque. This method of controlling the motor current is the same as the brushless DC motor control method, which is called the brushless drive method or Current closed-loop control method.

(2). The motor current is kept constant, and the method of controlling the phase angle between the exciting magnetic flux and the current is called the power angle closed-loop control method.
3. The internal structure of the motor
II.Stepper motor naming.
① Sub-series name.

Blank: no special meaning.

D: Product series larger than standard mounting base.

② Cabin seat No.

Motor installation size code (for example: 57 stands for 57 base)

③ Motor phase number

Blank: Two-phase hybrid stepping motor

3: 3-phase hybrid stepping motor

④ Motor type

CM: Cost-effective open loop stepper motor

⑤ Motor torque

Divided by 10 is the motor holding torque(for example:23 means 2.3Nm)

Note:20/28/35 divided by 100 is the motor holding torque

⑥ Design code

⑦ Standard custom code

A:Current parameter

⑧ Standard custom code

SZx: Double shaft type

BZx: Brake type

FSx: Waterproof type

0: No special meaning (x is a number)

⑨ Conventional custom code

S: Shaft extension change L: Lead wire change F: Shaft extension with platform N: Smooth shaft K: Shaft extension with keyway I: Shaft diameter change C: Lead wire with connector M: With synchronous wheel

⑩ Special application code
III. Stepper motor selection

1 .Stepper motor torque selection

The holding torque of a stepper motor is similar to the power called by a traditional motor. Of course, there are essential differences. The physical structure of a stepper motor is completely different from AC and DC motors. The output power of the motor is variable. Usually according to the size of the required torque (that is, the size of the torsion of the animal body to be carried), which type of motor is selected. Generally speaking, if the torque is below 0.8Nm, choose 20, 28, 35, 39, 42 (the diameter of the motor body, in mm). If the torque is around 1Nm, 57 motor is more suitable. When the torque is several Nm or more, it is necessary to choose 86, 110, 130 and other specifications of stepping motors.

2. Selection of stepper motor speed.

Special consideration should also be given to the speed of the motor. Because the output torque of the motor is inversely proportional to the speed. That is to say, the output torque of the stepping motor at low speed (a few hundred or lower speed per minute) is relatively large, and the torque (1000h rpm-9000 rpm) in the high-speed rotation state is very small. Of course. , Some working conditions require high-speed motors, and it is necessary to measure the coil resistance, inductance and other indicators of the stepper motor. Choose a motor with a smaller inductance as a high-speed motor, which can obtain a larger output torque. On the contrary, it requires low speed and high speed. In the case of torque, the inductance should be more than ten or tens of mH, and the resistance should be larger.

3. Selection of no-load starting frequency of stepping motor

The no-load starting frequency of a stepper motor is usually called “idling frequency”. This is an important indicator for purchasing a motor. If it is required to start and stop frequently in an instant, and the speed is 1000 rpm (or higher), it is usually necessary to “accelerate the start”. If you need to start directly to achieve high-speed operation, it is best to choose a reactive or permanent magnet motor. The idling frequency of these motors is relatively high.

4. Stepper motor phase number selection

Many customers pay little attention to the selection of the number of phases of the stepper motor, and most of them buy it casually. In fact, motors with different phase numbers have different working effects. The more phases, the smaller the step angle and the smaller the vibration during work. In most cases, two-phase motors are used more often. In the high-speed and high-torque working environment, it is more practical to choose a three-phase stepper motor.

5. Choose for the use environment of the stepper motor

Special stepping motors can be waterproof and oil-proof. For some special occasions, such as underwater robots, it is necessary to choose a waterproof motor. For special purpose motors, it is necessary to make targeted selections.